On account of Internet technology, which has been progressing further and further particularly in recent times, and all the associated communication and application solutions, it is possible even in command systems for controlling and observing a technical installation to spot the trend for developing such command systems by incorporating methods and solutions from the field of Internet technology.
The particular effect which is intended to be achieved by this is that the control stations (operator terminals) in the command system become largely locally independent of the site of the technical installation. In addition, the intention is for it no longer to be necessary to install special control and observation software on the control stations in order to be able to control the technical installation. A client computer with an installed web browser will be sufficient for this.
Such a command system allows a technical installation to be controlled remotely, and in many cases the control room within the technical installation no longer needs to be occupied or no longer needs to be occupied all the time.
In many known command systems, alarms within the technical installation are often reported not only by way of visual display, for example on a screen or a large screen, but also audibly, for example by way of a signal horn or a claxon. This, at least when an alarm message requiring rapid action appears, emits a loud tone at a particular frequency in order to give a clear indication to personnel present in the technical installation that there is an urgent need for action.
In an unmanned or only intermittently occupied control room, an audible alarm is inevitably often unnoticed.
In command systems which make use of Internet technology, a connection from a control station to a server computer in the command system is set up usually only when needed, for example in order to perform a control action or to assure oneself of the current operating state of the technical installation.
Such command systems usually have no provision for asynchronous transfer of messages from the server computer to a client computer (control station in the command system). Thus, in such command systems, it is essentially possible to transfer only such messages/signals to a control station (client computer) as are waiting on the server computer at the time of a connection existing between the control station and the server computer.